SITE INFORMATION AND CORRESPONDENCE

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Mr. Jeff Baker -2 - 17 Februa2011 Stockton Terminals Techni�ommittee ry Measurable separate phase hydrocarbons (SPH) have historically been observed in up to 20 wells. No measurable SPH was observed in any wells during the fourth quarter, but SPH sheen was observed in TS/M-2 and TS-4R. During the fourth quarter 2010, the highest dissolved COC concentrations generally occurred in A zone wells in the BP aboveground tank (AGT) area and in the southeast corner of the Tesoro property. In the deeper zones, maximum concentrations were encountered.on the Tesoro property in the TS/MW-1 D well CILIMer. The highest concentrations of TPHg and TPHd were in AR/MW-24A and AR/MW-10A at 80,000 micrograms per liter (Ng/L) and 240,000 pg/L, respectively. These high concentrations are consistent with recent maximum concentrations but less than the historic highs of 290,000 ug/L and 1,800,000 for TPHg and TPHd, respectively, observed in 2002 and 2009 in wells on the Tesoro facility. The highest concentration of benzene during the fourth quarter was detected in TS/M-2 at 11,000 pg/L. The highest concentrations of MTBE and TBA were detected in AR/MW-50 at 14,000 pg/L and 4,100 pg/L, respectively. Groundwater at the BP facility is polluted with MBAS. The water quality objective (WQO) for MBAS is 500 ug/L. To address the concentrations, BP over-purges (removes) up to 10 well casing volumes from wells containing MBAS before sampling. Table 6 shows that the maximum on-site MBAS detection during the fourth quarter was 5,400 pg/L in AR/MW-3A. The maximum off-site MBAS was 1,800 pg/L in OW-4C. During the fourth quarter,-BP over-purged 25 wells, and due to groundwater volume limitations, unsuccessfully attempted to over-purge an additional five wells. The Annual Report states that over-purging removed about 5,600 gallons of groundwater during the fourth quarter. Based on the continued presence of MBAS in four off-site wells (PS/MW-20C, OW-3CR, OW-4C, and OW-9C), Central Valley Water Board staff directed STTC to expand the MBAS sampling program to all Port of Stockton, Tesoro, and FTOC wells during the fourth quarter. Based on a premise that the MBAS observed at the Site has originated from leaky sewers and widespread industrial and domestic use in the area, Tesoro recommends delaying the requested analysis of MBAS in these additional monitoring wells in order to evaluate MBAS concentration trends and assess additional potential remedial options. Our 9 December 2010 letter concurred with the STTC's proposal to conduct an analysis of over-purged wells and sent a draft monitoring and reporting program (MRP) that requested widespread monitoring for MBAS, as well as diethylene glycol monobutyl ether (DGME), a chemical compound more specific to fire suppression foam. The Annual Report states that a response to the request and draft MRP are being prepared, but provides no specific date for submittal of the response. In the fall of 2004, the STTC began operation of two ozone sparge (OS) systems to clean up groundwater pollution migrating downgradient from the Site. The systems are comprised of 57 A zone and 16 B zone wells connected to two, 2 pounds-per-day (lbs/day) ozone generators. The OS system is divided into two portions. The west system is downgradient of Tesoro, and the east system is downgradient of BP. During the fourth quarter, the STTC estimates that the east system and west system had OS run times of about 68 and 45 percent, respectively. The reduced run times were